Hive - Is there a way to further optimize a HiveQL query?

Question

I have written a query to find 10 most busy airports in the USA from March to April. It produces the desired output however I want to try to further optimize it.

Ar

Answer 1

You can test this but you are in the case where an Union maybe better, so You really need to test it and come back :

SELECT airports.airport,
SUM(
  CASE 
     WHEN T1.FlightsNum IS NOT NULL THEN 1
     WHEN T2.FlightsNum IS NOT NULL THEN 1
     ELSE 0
  END 
  ) AS Total_Flights
FROM airports
LEFT JOIN (SELECT  Origin AS Airport, FlightsNum 
    FROM flights_stats
   WHERE (Cancelled = 0 AND Month IN (3,4))) t1 
 on t1.Airport = airports.iata
LEFT JOIN (SELECT Dest AS Airport, FlightsNum 
   FROM flights_stats
   WHERE (Cancelled = 0 AND Month IN (3,4))) t2
 on t1.Airport = airports.iata
GROUP BY airports.airport
ORDER BY Total_Flights DESC